OF THE ACALEPH.E OF NORTH AMERICA. 299 



THAUMANTIAS. 



On comparing the Fauna of the British coast with that of the United States, for 

 their Medusae, there appears a very striking difference between them ; for, though some 

 of the types occur on the two shores, there are others which seem peculiar to each. No 

 doubt this difference, great as it appears at present, will be gradually lessened as more 

 and more extensive investigations are made among the Medusae of the American 

 shores. Had not Professor Forbes devoted so many years to the study of this class, 

 we should certainly be unacquainted with so great a diversity of British Medusaj 

 as he has so well described. However, the occurrence of so large a species as Stau- 

 rophora among the few Medusae noticed on the shores of Massachusetts, when 

 nothing of the kind has been noticed on the shores of Great Britain, after the 

 thorough search made by Professor Forbes and Captain McAndrew, indicates 

 plainly that the two countries do not agree fully in their Acalephaean Fauna. We 

 have here Aurelia, Cyanea, Rhizostoma, and Pelagia among the large Medusae, as 

 they occur also on the shores of Great Britain ; but no Chrysaora, nor any Cassiopea, 

 has yet been found here, nor have representatives of the genera Willsia, Circe, Oceania, 

 Saphenia, Turris, Stomobrachium, Tima, Geryona, Slabberia, Moderia, Geryonopsis, 

 Lizzia, Steenstruppia, and Euphysa been found. But here we have Staurophora, which 

 does not occur there ; and the genus Thaimiantias, of which so many species have been 

 discovered on the British shores, has yielded only two representatives on the American 

 shores, up to the present day ; while a species closely allied to Thaumantias is found in 

 great abundance on the shores of Massachusetts, but differing from the true Thaumantias 

 in peculiarities striking enough to constitute a genus by itself, of which no analogous 

 representative has yet been found elsewhere. For that genus I have proposed the name 

 of Tiaropsis, alluding to the peculiar form of its eyes, which are not connected with 

 the tentacles, but alternate with them, and are surrounded with a crown of globular 

 vesicles, forming a diadem above the black speck. Another genus peculiar to the United 

 States is my Nemopsis. The first species of Thaumantias proper which I observed 

 in this country was caught off" Gay Head, and in Edgartown harbour, under circum- 

 stances which did not allow me to have it drawn with sufficient details, and to in- 

 vestigate its structure with any degree of accuracy. All I could do was to ascertain 

 that it truly belonged to the genus Thaumantias, having round the margin short ten- 

 tacles with an eye-speck at their base, the tentacles being alternately longer and 

 shorter, one of the longer arising from the base of the four radiating chymiferous 



